1. Field of the Invention
The invention relates to a vehicle interior component and, more particularly, to an improved technique for fastening, for example, an upholstery or a noise insulator to a back side of an interior base material with fasteners.
2. Description of the Related Art
There are widely known vehicle interior components such as a door trim and an instrument panel. In the vehicle interior component, a member that is fastened to a back side of an interior base material (hereinafter, referred to as “back-fastened member”), for example, an upholstery or a noise insulator is fastened to the back side of the interior base material with fasteners. A vehicle interior component described in Japanese Utility Model Application Publication No. 4-24333 (JP-U-4-24333) is an example of such a vehicle interior component. In this vehicle interior component, a thick-walled portion is formed at an outer peripheral end portion of an interior base material made of, for example, synthetic resin material. Then, fasteners are driven into an end portion of an upholstery, made of, for example, felt with the end portion overlapped with a back side of the thick-walled portion, whereby the fasteners are engaged with the thick-walled portion. Thus, the end portion of the upholstery is integrally fastened to the interior base material.
As shown in FIG. 4, an upholstery 102 is stuck onto a front side of a resin interior base material 100, for example, a door trim, and an end portion 104 of the upholstery 102 is folded toward a back side 108 at an outer peripheral end portion 106 of the resin interior base material 100 and is overlapped with a thick-walled portion 110 formed along the outer peripheral end portion 106. In this state, a fastener 112 is driven from the back side 108 through the end portion 104 into the thick-walled portion 110. Thus, the end portion 104 is integrally fastened to the thick-walled portion 110 of the resin interior base material 100.
However, in such a fastening structure, the following problems may occur because the thick-walled portion is partially formed. For example, deformation such as warpage easily occurs due to, for example, a difference in contraction between the thick-walled portion and a thin-walled portion, and shrinkage may cause poor appearance of an outer surface (front side) that is a decorative surface. In addition, a forming cycle is prolonged. To address this problem, the size of the thick-walled portion 110 may be reduced as shown in FIG. 5A, for example. However, as shown in FIG. 5B, if the position at which the fastener 112 is driven into the resin interior base material 100 (hereinafter, referred to as “fastener-driven position” where appropriate) deviates to the thin-walled portion (center portion of the resin interior base material 100), the fastener 112 may be easily disengaged from the resin interior base material 100, and a needle tip of the fastener 112 may protrude from the outer surface.